Note 1 to entry: A balun is used, for example, to couple a symmetrical antenna to an unbalanced feed line.

Note 2 to entry: The term "balun" is derived from “balanced to unbalanced transformer”.

Note 3 to entry: A balun can be realized in practice by using a transformer or a lumped parameter or distributed parameter network, which can include active devices.

Note 4 to entry: A balun can exhibit inherent impedance transformation differing from unity.